Abstract

The effect of exposition time (time between the installation of traps and the collection of spiders) and
autumn air temperature on spiders overwintering on tree bark was studied in a planted black pine forest
(Pinus nigra) near Debrecen (east Hungary). We collected spiders from traps fixed 2 m high on tree
trunks once every five days for 50 days in 1999 and 2000. We collected 957 spiders belonging to 15
species and 1 species determined to the genus level in the two years combined. In 1999, the diversity
and number of spiders increased with exposition time but were not influenced by temperature when
data were combined for each sampling time. This was because temperature was low in the middle of
the sampling period, but increased again at the end, which weakened its effect. However, the diversity
and number of individuals continued to increase even when temperature increased at the end of the
sampling period. In 2000, the number of individuals increased by exposition time because we found individuals
of Philodromus margaritatus in very high numbers on the last sampling occasion. There were no
other differences in 2000 because temperature was constantly high during the sampling period. Our
results suggest that the movement of spiders to the bark is a characteristic process and that the diversity
and number of spiders continue to increase in the autumn even when temperature slightly increases.
This process, however, can be delayed if temperature is constantly high during the study period.